Concerning Multiverse Theory
by Stunt Muppet
Summary: He indulges, for a moment, in abstraction. The Third Doctor and Section Leader Elizabeth Shaw from Inferno , and the equations of possibility. Three/Section Leader Shaw.


A/N: AU missing scene from _Inferno_, roughly taking place in the scene between the Doctor and Section Leader Shaw in the prison cell in Episode Four.

* * *

Premise: There are many worlds, many universes, each one slightly different than the other.

(Seems a reasonable enough assumption, given that he's fallen into one of them.)

Current multiverse theory — or at least the last of it he'd heard — dictates that contrary to popular belief multiverses do not split from the parent reality at every arbitrary choice. Rather, a certain threshold of potential change must be reached to trigger fracture. In simpler terms, it's the big choices that count — to end a life or to spare it; to tell a secret or to keep it; to venture across the void or to stay and continue his repairs. Not that it's always so obvious what those big choices are.

(Are there fractures, then, between the worlds as well? Is there a void he left behind and a void he never escaped? He might not have completed the journey. Possibly this had already been answered, during one of the Theoretical Physics lessons that he hadn't paid attention to.)

But even the choices with a sufficient quantum of potential do not affect every living thing — indeed, some may only be significant to the life of a single person. As such, there are overlaps between the universes; for any given fracture the majority of planets and people and places and history will be identical. Most humans, for example, would be genetic duplicates of their counterparts in other realities. Some differences due to random recombination can probably be accounted for, unless they result in a significant physical or mental deformity of some sort.

(To put it more practically, a change from redhead to dark brunette is not quite important enough to split a timeline down the middle.)

Therefore, for those who are not physically affected by a choice, any differences in thought processes or personality between homologous humans in different realities must be a result of other, outside changes. The consequences of a choice change the environment in which a human being lives, which in turn precipitates changes in behavior.

Proposition: Might there be some way to quantify these changes? Is there a way to calculate how many fractures enact a significant difference in a human? Might there be some percentage of what remains the same?

(She sounds like her, looks like her, feels like her right down to the bones — for he has come to recognize the clean lines of the patellae, the clavicle in sharp relief, the faint protrusion of the lower rib as she takes in a single, sharp breath. But what could be left of Liz in this woman?)

(Or, conversely, what is left of her in Liz?)

(Slim fingers — precise as scalpels, just as before — grip a fistful of his hair, and she again demands his name.)

The equation would be immensely complex, surely, even for him; in order to establish the range of variation in a single individual, you'd need to take into account all possible realities in which they exist, even those where divergence occurs in some other corner of the universe and leaves them untouched. And then there would have to be some method of gauging the change in the person in question.

Is such a thing quantifiable at all? The theorists of Gallifrey would say that it is, given proper controls and accurate measurement.

(He'd laughed at the idea then and it's just as foolish now. What increments are there, then, for mercy or cruelty, intuition or reason? How would you measure the cold and brutality he'd never have thought her capable of — or the dexterous mind that couldn't be stifled, even here?)

(But watching her, you could almost believe that such a percentage existed. She pins down his legs and shoulders and hisses _who are you, look at me, answer me_, but something remains in her that doesn't feign struggle, that sees the inevitable around her and says _you were right about the computer, what else are you right about, what do you know?_)

Or perhaps calling it a percentage is going about it the wrong way. To measure the degree of sameness implies that there is only one iteration of that person who serves as the template, who is correct while all the others are aberrations. A common fallacy.

Perhaps every permutation of a person across the fractured possibilities is only a facet of a larger whole. Perhaps sentient beings exist in superposition, a cluster of everything they could ever be. It remains to circumstance to reveal which aspect of them actually exists in any given reality.

(The scientist he knows is hidden somewhere in this soldier's brain, masked by a slight shift in timespace.)

(He clutches at her jacket, unfastened and loose on her back; he pulls her down against him and tells her everything.)

It's unlikely that this difference percentage could ever be a true equation, even in theory. It's too imprecise and requires far too much data. But it is a respite, at least, from the simpler problems that he's solved long ago — the velocity of the drilling, the rate of penetration, the speed at which a human being reverts to a monster.

(Hours, they have only hours, and by now there may be no way to stop it, not while he's stuck in here. Those few solutions he's devised have a marginal chance of success at best — they'd have had to stop drilling half an hour ago for the Earth's crust to remain stable.)

(The forces at the planet's core will burst out no matter what he does. Inevitability, in elegant physics.)

For the time being it's a relief to have something more abstract to occupy his mind.

(He thought, at first, that she might be distraction enough, this woman who might've been Liz. A waste of valuable time, yes, but when she unlocked the cell door he had been…tired. Exhausted, really. Sick of fighting his way out of one prison only to land in another.

She started out calm and even reasonable, but maybe she knew how little time there was, because when he refused again and again to tell her what he did not know she lost patience. She'd seized him with one hand by the collar and stared him in the eye and told him to sit down, right now, because one way or another he was going to tell her what she wanted to know.

She, not they.

He didn't push her hand away.

_Surely you don't really need to know who I am before you execute me,_ he'd said, as he sat back down on the cot. _Or is that one of the required boxes on Form C?_

_We need to know if it's necessary to make an example of you._ Her voice was cold but he saw in her the same glassy expression Liz assumed when she was trying not to look curious. Strange that that, of all things, should remain the same. _Now, your name._

_Must we do this again?_

_Who are you?_

_I've told you already; I've told you a thousand times._

_You have lied to me a thousand times. Don't insult me by doing it again._)

Besides, if he continues from the premise that every possible outcome of a significant ambiguity is explored in a divergent reality, then in some other world some other him has already escaped, or never become stuck here at all. He'll have to take another sideways trip, he thinks humorlessly, and ask him how he did it.

Or maybe he'll be the one that breaks free, while a different him burns with the Earth.

(She kept up the pretense of interrogating him: pushing him onto his back, stripping off his jacket and tie like she was skinning him alive, questioning for as long as she could speak. And why not? Let her think herself whatever she likes, if it gave him a moment's peace from the temperature and the velocity and the countdown.

It wasn't any use, of course. She is too different and too much the same; everything she is and could be charges her skin like static. So instead he clutters his mind with theory and tries to calculate just how different she really is.)

Hence, according to prevalent thinking, the existence of a multiverse does not preclude free will. No individual can know the outcome of their actions, how different our divergence will be from any other, or whether or not they will cause divergence at all. We proceed without instruction, becoming more and more possibilities.

Admittedly, that aspect of the theory has never sat particularly well with him. It seems too easy a solution for something so critical.

(She rises at the end without a word and turns her back to him as she buttons up her shirt. _If you wouldn't persist in telling these fairy tales_, she finally says, unlocking the cell door, _I might have been able to spare you the firing squad._

_Firing squad? Not much of an example you're making, is it? I'd have thought at least a public hanging._

_Still joking. I don't think you're quite taking this seriously, Doctor; your execution will be approved within the hour._

_Then why bother to help me?_ She doesn't answer, but she doesn't leave, either. _Perhaps because you know there_ is _something wrong?_

She glances back at him, holding the door half-open. _You'll be given one last chance to confess before the execution,_ she says, and her voice is as hard as ever it was. _I suggest you consider your options._

She walks out, locking the cell door behind her.)

What if he does return to his universe, and it's already too late? What if the outcome has already been decided — had been, from the moment he left? What if that was his choice, the only choice?

What about the Doctor that never slipped across the void in the first place? Would he stop the project? Or had some even earlier fracture locked him in place as well?

Conclusion: Theory provides no answers here.


End file.
